Bump-Starts and runs great, won't start with key - P0335 - ECU replacement fixed

Nothing that would affect RPM, the Cam and Crank sensor inputs are solely responsible for that.

If it was low voltage I would expect the ECM to stop communicating.

 

I read through a bunch of the posts, and notice the focus is mostly on the crankshaft and camshaft sensors and ECU.

Along the lines of hyharari's question...
Could this be related to ECM security somehow (chipped key, etc.)?
And, is there any aftermarket security or remote start modules installed?

 

My key is the simplest, just a metal shape, no chip/modules or security installed (was thinking of the latter at some point).


So I finally got a bump start scope reading, sorry about the cutoff, I was expecting 5V would be enough but was wrong:


Stupid me I immediately turned the engine off (from so many cranking with the scope next to me in the last days, became an instinct).
When I tried bump starting again, it refused to start!
Just like what happened to me in post #1

I thought maybe the probes got loose so I removed them completely and tried again, still no bump-start -weird.
What I think may have contributed is that I never turned the key completely out.
Since the first bump start , then shutoff to acc, then tried again cranking, then bump starting couple times.

*now I got to haul her uphill and try again.

Edit: I verified again, got a p0335 code once started...
I clear all codes every time to see if anything specific is triggering.

Also, I can really "feel" the engine is starting right at the first little "bump", not needing many revs at all. If I were to guess, I'd say the "starting" happened around 550-600 ms and the rest was the engine on its own.

Oh and here's a cold crank right before the bump start to make sure everything is wired right:

 

Did you save the raw waveform files from the start and no start?
If so please zip them up and post them, there's only so much we can tell from a picture of them.

 

There's nothing that should affect the ECMs ability to sense the Cam and Crank signals, communication with the ECM is good but we have 0 RPM. Even if the Immobilizer (which it doesn't have) was active we would still have an RPM signal.

 

Forgot that, here:
The "bump" file is the one that got the engine running, the rest failed.

PS: I have all the different test readings I've done before (mentioned or posted) saved..

 

I can't open the .psdata files.

But i see the cam/crank signals look "noisy" on the crank with key.
And we still have 2.5ish volts.
and the crank signal is not "consistent" voltage wise across the whole waveform.

The push start looks "cleaner" and we are back to 4.5v - 5v. (Looks good)

 

So I bumped again and fired right up, I guess needed just a bit more speed.

That's weird, maybe zipping corrupted them?
I'm using Software 7, maybe that has to do.

I think the noise is just due to the larger zoom used,
Sorry the reading aren't in the same scale/zoom so can be misleading.

 

I'll have a look when I get time although it will probably be tonight before I have a chance to look at them in detail.

 

Grab Pico 6 it's free and will run on pretty much any PC.
https://www.picoauto.com/downloads

 

I'm still just trying to think outside the box....
So could a week battery cause the issue (voltage dips too much running the starter)?
No big load on the battery when bump starting.

 

I got the software.
I was able to open the files.

The cam / crank are the same correlation. So timing looks good.

But when cranking with the key. The crank signal is weak and wave.
I don't do this for a living, and I don't look at waveforms often.

But the crank signal just looks "weak and sick" when cranking.
But why? I have no idea.

Is something drawing the signal down when cranking?

 

I mean @Dm93 says 2.5v should be enough for the ECM to see the crank signal/

But I don't know?

That's the only difference I see......

As for battery voltage.
No. If it can crank the engine, it should start.

 

Possibly but measuring the signal looks like we have around 200-250 RPM cranking speed which should be more than enough.

I would think that it should be but apparently it's not, looks like +/- 3v is the magic place where it decides to fire.
I guess we need to investigate the crank sensor anyway and see if anything is amiss there.

 

So at this point maybe worth a try replacing it again?
I already got a Denso one around 100 bucks from ebay, wondering how annoying will it be with the compressor in the way.
Any tips on that job are welcome, is it possible to move the compressor aside while keeping its lines connected?


*Note: I tested my battery voltage using a multi-meter and I get around 12.5V which drops to 11.25V (stable after a while) while cranking.

 

Yeah, you should be able to leave the lines connected to the compressor.

What brand did you replace it with before?

 

The detection distance for a hall-effect sensor is usually critical. Could the crank-shaft sensor not be mounting close enough to the tone-wheel? Or, is something magnetic close to the sensor?

Sorry, no answers just questions.

 

Certainly distance from the tone wheel affects signal amplitude, typically the only thing that affects that distance is incorrect sensor, improper installation, or rust jacking.

I'm puzzled that 2v isn't enough amplitude for the ECM to "see"the signal though, should be more than plenty.

 

Another thing that came to mind is maybe some motion sensing can override something?
I doubt it but at this point, who knows.

I think I'll try replacing the ckps sensor again tomorrow.
Should I clean inside while I'm at it? Spray some break cleaner?

I don't know which ckps brand they put, was one (or both) of the mechanics, and I don't have my hopes up either but heck this is really driving me mad.

Here's some live data while idling warm just in case something pops up to someone:

 

When was the CKP sensor replaced?
Before or after the guy used the TORCH and BROKE the AC compressor off?

Did the truck start the long crank issue after the AC incident?

I can't figure out how the signal is healthy when NOT using the key.
But the signal is good when running or bump starting.

I'm trying to figure out how (or what) we can test while cranking.
I'd want to test ALL theories before replacing the CKP sensor.

Would pulling the STA fuse, then checking powers/grounds at the ECU be worth it?
I want to know what is happening in the circuitry cranking with NO crank signal. Just to see......Why not?

I think we know WHY the truck wont start. (amplitude)
But what we don't know is, what is causing it.